Instead of a conventional thermostat valve and a conventional coolant pump driven mechanically by the internal combustion engine, this method uses an electrically controlled bypass valve and an electrically driven coolant pump. In this case, the rotational speed of the coolant pump and the setting of the bypass valve are regulated as a function of the coolant temperature at the outlet of the internal combustion engine and by the difference between the coolant temperatures at the outlet and inlet of the internal combustion engine.
With this method the rotational speed of the coolant pump can be minimized to keep the energy consumption of the coolant pump as low as possible. However, the resulting restricted flow rate of the coolant results in relatively large idle times of the system. This is particularly serious if the bypass valve is located in the vicinity of the outlet of the internal combustion engine. This results in very long delays until the coolant is available at the inlet of the internal combustion engine (e.g. for cooling the internal combustion engine) after the setting of the bypass valve has been changed. In the case of short-term increases in load, such as those that occur, for example, when a motor vehicle fitted with this arrangement is involved in overtaking, this may lead to the coolant not reaching the inlet of the internal combustion engine until the overtaking process has already ended.